1. Field of the Invention
The present invention relates to data processing of digital image.
2. Description of Prior Art
A digital image is subjected to various kinds of image correction. Image correction is performed on various items such as lightness, saturation, sharpness and contrast.
When an image is dealt in a color space such as HSL space, the range of saturation (S component) depends on lightness (L component). Therefore, when saturation is converted, maximum saturation and lightness are taken into account. For example, in an apparatus described in Japanese Patent laid open Publication 9-18727/1997, by considering the difference in color reproduction range between input and output apparatuses, a color outside the color reproduction range is compressed to a color inside the color reproduction range, in order to keep the tone of an input image. Therefore, imaging direction is determined based on hue, lightness and saturation of input color. Especially for an image including colors of high saturation, color change in an output image is not noticeable.
In image correction, contrast correction using lightness component is known. However, it has a following problem. When lightness is increased in contrast correction, saturation seems to be decreased. Further, if the saturation is changed by the same amount for all lightness value, the saturation is observed differently, depending on lightness. Therefore, it is desirable to take saturation change into account in the contrast correction.